1. Technical Field
This invention relates to biomedical probes, and more particularly to neural probes of the type having an electrode extending distally from a semiconductor base.
2. Background Information
The use of semiconductor-based neural probes has begun to replace the use of prior wire bundle probe systems. In a broad form, the probe elements in such systems comprise a semiconductor substrate base with one or more electrodes. More precisely, such a probe may have electrode-bearing shafts extending distally from the forward edge of the semiconductor base.
As shown in FIG. 1, the probe element 10 is preferably held by a micropositioner 12 which facilitates the precise introduction of the electrode-bearing shaft 14 into a desired area. Shaft 14 is usually introduced into a neural mass 16, such as a target brain region under study in the laboratory. A processing unit 18 is provided to receive electrical signals from and provide electrical signals to the probe element.
To provide mechanical connection between the probe element 10 and micropositioner 12, the probe base is adhered to the surface of a circuit board 20 adjacent its forward end. Electrical communication between the probe element 10 and processing unit 18 is effected by wire bonding techniques which are used to connect contact pads on the probe base to associated contacts on the circuit board. A cable 22 may then be provided to connect the circuit board to the processing equipment. This completes the electrical path from the electrodes to the equipment. The probe base may be encapsulated by applying a drop of encapsulation material atop the base so as to protect the wiring and further secure the base to the circuit board. The circuit board is also attached to the micropositioner 12 such as by mounting the circuit board on a base 24 which is connected to the micropositioner by means of a shaft 26.
Such systems may be unduly cumbersome. Additionally, the encapsulation material which is applied to cover the base may bend the electrode-bearing shafts as it hardens. This can create further alignment problems. Alignment is critical for accurate and precise insertion and guidance of the electrodes to their targets. The shafts should all be parallel to each other and parallel to an insertion axis of the micropositioner.
Accordingly, it is desirable to provide a compact and robust system for providing precise alignment of the electrode-bearing shafts of a probe with the axis of a micropositioner.